During the first year of this project we tested the feasibility of our procedure of localizaton of adenylate cyclase at the electron microscope level in mouse and human testes (Chakraborty and Nelson, Biology of Reproduction, in press) and secondarily prepared the groundwork for an examination of the effects of hormonal stimulation on the adenylate cyclase activity in mice and human testicular tissues. During current year we localized the adenylate cyclase activity in immature (22 days old) mice testes after injecting them with FSH, LH and/or testosterone propionate (TP). Stimulation of adenylate cyclase was observed in the plasma membrane, cytoplasm and within the nucleus of early and late spermatids when the mouse was injected with testosterone propionate. Stimulation of the enzyme was noticed in the plasma membrane of the early spermatids in LH and testosterone treated animals. Sperm tail adenylate cyclase was stimulated in mice injected with FSH and testosterone. FSH, LH and testosterone injections greatly stimulated the adenylate cyclase activity in basal lamina of the seminiferous tubule and in the plasma membrane of the early and late spermatids. Sertoli cell enzyme was also stimulated to a small degree. From our above experiments we have concluded that: a) adenylate cyclase in the immature mouse testis can be stimulated by hormones, b) different hormones act differently upon male germ cells depending upon their stages of differentiation. Employing our technique, we shall be able to interpret more conclusively the role of various hormones at specific cell sites for differentiation and maturation of male germ cells and maintenance of normal testicular function, which may shed further light on the problem of human male infertility due to impaired testicular function.